High-speed shared channels for downlink and uplink transmissions are available in third generation partnership project (3GPP) Release 6 systems. Currently, these channels are only available when a user equipment (UE) is in a Cell_DCH state. The UE is in the Cell DCH state if dedicated channels are allocated for the UE. In other radio resource control (RRC) states of the connected mode, (i.e., Cell_FACH, Cell_PCH, and URA_PCH states), the UE is not allocated dedicated channels. Communication with the UE takes place over a random access channel (RACH) and a forward access channel (FACH) in the Cell_FACH state, and over a paging channel (PCH) in the Cell_PCH and URA_PCH states.
FIGS. 1 and 2 show conventional medium access control (MAC) entities in the network and in the UE, respectively. A plurality of sub-MAC entities are included in the MAC entity. The MAC-b entity controls a broadcast channel (BCH). The MAC-c/sh/m controls access to all common transport channels, except a high speed downlink shared channel (HS-DSCH). The MAC-d controls access to all dedicated transport channels to MAC-c/sh/m and MAC-hs. The MAC-hs handles high speed downlink packet access (HSDPA) specific functions and controls access to the HS-DSCH. The MAC-e/es controls access to an enhanced dedicated channel (E-DCH).
The data rates available on the FACH channel in the downlink are in practice limited to low values due to the inability of a radio network controller (RNC) to modify its transmission power or a modulation and coding scheme to adapt to the requirements of the different UEs served by the FACH. This data rate limitation means that the duration needed to set up dedicated channels for the UE is relatively long and this, in turn, results in long call setup times which degrade end-user experience. Because of this, it has been proposed to allow the use of the HS-DSCH while the UE is in the Cell_FACH state. It has also been proposed to allow the use of the HS-DSCH for paging in the Cell_PCH and URA_PCH states.
While allowing the utilization of the HS-DSCH in the Cell_FACH, Cell_PCH, and URA_PCH states would improve the system performance, there are a number of issues that need to be solved in order to avoid inefficiencies. MAC architecture should be modified to allow the utilization of the HS-DSCH in other RRC states. MAC sub-entities should also be modified to solve the following issues: how to efficiently identify UEs that the data carried over the HS-DSCH belong to; how to efficiently identify types of logical channels that the data carried over the HS-DSCH belong to; and how to handle legacy UEs that do not support the feature.